Table of Contents

At a glance

The highest number of hot days averaged across Germany were recorded in 2003 and 2015.

Despite considerable fluctuations between individual years, the overall trend is rising significantly.

More hot days are expected during summer months in the coming decades due to climate change.

Environmental importance

Rising temperatures can adversely affect human health. The Deutscher Wetterdienst defines the ‘hot day’ as any day on which the maximum temperature exceeds 30 degrees Celsius (°C).

High air temperatures have a direct impact on the human body, as the heat can cause circulatory problems. Indirectly, hot weather can raise pollutant levels in the air we breathe, leading to an increase in respiratory and circulatory diseases. High air temperatures combined with intense sunlight encourage the formation of ground-level ozone. Ozone irritates the eyes and airways and can exacerbate existing respiratory diseases. It can also trigger allergic reactions.

Assessing the development

In 2017 Germany recorded just under seven ‘hot days’, when temperatures exceeded 30 °C.

The strain on heat in 2003 and 2015 was particularly high: in these years there were 19 respectively 18 ‘hot days’. Seven of the ten hottest years based on the number of hot days were recorded between 1994 and 2015. Although the annual figures for this indicator vary greatly, the overall trend has increased significantly since records began.

Climate models show that in future Germany can expect an increase in the number of hot days in summer and more prolonged heat waves.

Methodology

The indicator is based on temperature measurements taken at Deutscher Wetterdienst (DWD) monitoring stations. Temperature readings and indicator values must be calculated for those areas not covered by monitoring stations. The results can be presented in a grid (1×1 km) which shows the distribution. An annual total of hot days is calculated for each grid point. The indicator is the mean of the annual values for all grid points (areal mean). More information about the calculation method can be found at Müller-Westermeier (1995, in German only).

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The Umweltbundesamt

For our environment

The impact of climate change will be felt more strongly in the future – and in Germany too. This is the conclusion reached in what is called the vulnerability analysis, a comprehensive study on Germany's vulnerability to climate change.